The Maryland Refutation Proof Procedure System (mrpps)

The Maryland Refutation Proof Procedure Systems (MRPPS) is an interactil perimental system intended for studying deductive search methods. Although the work is oriented towards question answering, MRPPS provides a general problem solving capability. There are three major components within MRPPS. These are: (1) an inference system, (2) a search strategy, and S (3) a base clause selection strategy. The inference system is based on the resolution principle and performs the logical deductions specified. The user may select from a wide variety of refinements of resolution. Current refinements are: set of support, linear, P1, SL, input, and combinations of the above. Paramodulation and deletion by tautologies and subsumption are also provided with the system. The search strategy directs the deductions to be made by selecting from clauses already generated those that have. the best merit. The merit of a clause is given by f(n) = wog(n) + wihi(n) + w2h2(n) + + wkhk(n). If the user can specify tie-breaking rules for equal values of clause merit, an upwards diagonal search results in the sense of Kowalski. The upwards diagonal search included in MRPPS generalizes the Kowalski upwards diagonal search to an n-dimensional search. The base clause selection strategy determines which facts and general axioms to select from the data base. Such a clause may be selected regardless of whether or not it has the best merit. Heuristic techniques are applied within each of the three major components. This technical report describes the current implementation of MRPPS. It describes each of the components and how they are integrated into what has been termed the Q* algorithm. HIPPS is written in FORTRAN V for the UNIVAC 1108 (a version of FORTRAN IV) and runs under EXEC 8 at the University of Maryland. The current imp'mentation is core bound and requires approximately 60K words of memory to run, of which 35K is for the data base and for working storage.